BORE VS STROKE ?

[remedusakti]

Buat Master2 Smers, tolong ada yang bisa jelasin nih.
kalau ngeliat mesin2 mobil sekarang, keliatannya produsen buat satu tipe mesin untuk lebih dari satu ukuran ( kapasitas ).
Contoh
- Mesin Xtrail seri QR 20 dan 25, kalau diliat speknya diameter pistonya sama persin namun yang membedakan adalah strokenya, tipe QR25 lebih panjang dr QR20 so Volume ( CC ) membengkak jadi 2500cc.
- Mesin Nissan seri MR18( livina 1.8 ) dan seri MR20(all new xtrail), diamter sama cuma MR20 lebih panjang strokenya.
- Mesin Honda seri L15A ( city or jazz ) kalau diluar kan ada tipe L12/13, L14 ( sorry kalau salah), itupun sama sama diameter tapi beda stroke
- Mesin Honda seri R civic 1.8 dan CRV 2.0, juga sama diameter beda stroke.

kalau menurut temen2 SMers, lebih untung mana yah diameter kecil stroke panjang, dibanding dengan diameter besar tapi stroke pendek ?

[ZombiEE]

katanya kalo buat balap jgn yg stroke tinggi..langkah tinggi malah ga kuwat stang dan pistonnya ntar?ntah lhar..hehehehe

[imsus2c]

wah...saya mo tulis reply jadi nggak pede nih...pak TS kan nanyainnya ke para master...sy masih jauh dibilang master

menurut obrolan mekanik:

Kalo diameter bore/piston angkanya lebih besar dari langkah/stroke, tipe ginian biasanya disebut Oversquare Engine. Dengan rasio ini, piston mesin bisa dipacu ke RPM yang lebih tinggi dan umumya power outputnya juga lebih tinggi. Istilah awamnya, tenaga dan torsi ada di putaran "atas".
Resiko keausan mesin (engine wear) lebih dikit. Konstruksi model ini, rasio kompresi juga relatif lebih rendah. Dan menurut beberapa pengalaman, konsumsi BBM untuk mesin tipe ini relatif lebih boros plus emisi tinggi.
Karena karakter rpm dan power output, mesin ini sering diaplikasikan ke mobil buat balapan dan cruising.

Kalo diameter bore/piston angkanya lebih kecil dari langkah/stroke, disebut Undersquare Engine.
Keuntungan dan kerugiannya yaa kira-kira kebalikannya dari Oversquare Engine yg diatas...jadi ngga perlu panjang lebar ditulis kan?

Nah...untuk menyeimbangkan karakter plus/minus dari 2 tipe diatas, dibuatlah tipe Square Engine, alias angka diameter bore/piston relatif sama dengan angka di langkah/stroke.

[GTR]

bener,
kalo diameter makin besar cenderung (relatif) ke power daripada torque.
kalo langkah piston yg cenderung panjang, sama pengaruhnya ke cenderung "lebih" panjangnya poros engkol(crankshft) makin mudah bagi tenaga mesin unutk "memutar engkol/crankshaft" tsb; simplenya engkol sepeda yg makin panjang akan lebih makin mudah di"kayuh" daripada yg lebih pendek dengan dorongan kaki(torsi) yg sama.

kebanyakan produsen mobil "memainkan" panjang langkah piston dlm memperbanyak varian kapasitas mesin daripada "main" diameter; krn cara ini lebih flexible dlm rentang perbedaan kapasitas drpd "main" diameter.
karena itu pula jadi masih bisa menggunakan blok (model share) yg sama utk maintain jarak yg ideal antara silinder2 di suatu blok mesin.
paling tidak, parts yg utama adalah setang piston lebih pendek dan crankshaft yg lebih panjang utk basis blok model share.

kekurangannya pd rpm tinggi:
makin panjang langkah piston, makin sulit maintain clearance dan juga blok mesin seolah makin "twist" sehingga vibrasi lebih mungkin meningkat.
Piston speed jadi tinggi, gesekan tinggi.

[remedusakti]

@bro GTR n Imsus2C, kira2 kl untuk pemakaian sehari2 lebih bgs mana ya? kl gw liat dimajalh autobild xtrail mesin MR20 stroke panjang akselerasi lbh baik drpd QR20 stroke pendek.
kalau engine oversquare n square kalau ditune buat balap lebih bgs drpd undersquare?

mengenai vibrasi, gw coba gigi netral xtrail2.5(under square) diinjek gas ampe 2000 rpm geteran mesinnya lbh berasa drpd crv 2.0. bgt juga city (under square)geterannya lumayan berasa ketimbng crv. mungkin apa pengrh perbedaan bore n stroke ?

[maxx]

Dari wikipedia neh.

Bore/stroke ratio
===============

Bore/stroke is the most commonly used term, which is mainly used in the USA, Great Britain, Australia and some other countries.
An engine that has wider bore vs. stroke has a bore/stroke value of over 1.
For example an engine which has 100 mm (millimeter) bore and 80 mm stroke has a bore/stroke value of:
100 mm / 80 mm = 1.25
Such an engine is referred as oversquare or short-stroke engine.
An engine that has shorter bore vs. stroke has a bore/stroke value of under 1.
For example an engine which has 90 mm bore and 120 mm stroke has a bore/stroke value of:
90 mm / 120 mm = 0.75

This type of engine is called an undersquare or long-stroke engine.

An engine that has equal bore and stroke has a bore/stroke value of 1.
For example an engine which has both 95 mm bore and stroke has a bore/stroke value of:
95 mm / 95 mm = 1.00
This type of engine is called a square engine. Usually engines that have a bore/stroke ratio of 0.95 to 1.04 are referred as square engines.

Oversquare
=========
A piston engine is oversquare or shortstroke if its cylinders have a greater bore (width, diameter) than stroke (length of piston travel). This is generally considered to be a positive trait, since a shorter stroke means less friction and less stress on the crankshaft. An oversquare engine is generally more reliable, wears less, and can be run at a higher speed; though with the aid of modern technology, the disadvantages of undersquare or longstroke engines have been overcome. In oversquare engines power does not suffer, but low-speed torque does to some degree, since torque is relative to crank throw (distance from the crank center to the piston pin center)—the leverage, essentially. An oversquare engine cannot have as high a compression ratio as a similar engine with a lower bore/stroke ratio, and using the same octane fuel.[citation needed] This causes the oversquare engine to have poorer fuel economy, and somewhat poorer exhaust emissions.[citation needed] Engines can be modified by being "de-stroked", shortening the stroke to increase maximum rpms and top-end horsepower, at the expense of low-end torque.

Oversquare or shortstroke engines have a tendency to overheat[citation needed], but modern designs usually compensate for this tendency. Oversquare engines are lighter and shorter than similar undersquare engines along the direction of piston travel, but they are wider in directions perpendicular to piston travel. As the length is not a large problem, these engine types are highly favored by many manufacturers because of their power and compact size.

Formula One engines have a bore to stroke ratio of approximately 2.5:1 and are capable of revving to 19,000 rpm[citation needed].

Undersquare
==========
A piston engine is undersquare or longstroke if its cylinders have a smaller bore (width, diameter) than stroke (length of piston travel). This can be a negative trait, since a longer stroke usually means greater friction, more stress on the crankshaft, and a smaller bore means smaller valves which restricts gaseous exchange; however, with the aid of modern technology, these are not the large problems that they used to be. An undersquare engine usually has a lower redline than an oversquare one, but it may generate more low-end torque. In addition, a longstroke or undersquare engine can have a higher compression ratio with the same octane fuel compared to a similar displacement engine with a higher bore/stroke ratio. This also equals better fuel economy and somewhat better emissions. An undersquare engine does not overheat as easily as similar oversquare engine. Engines can be modified with a "stroker" crankshaft, which increases an engines stroke from stock, increasing torque.

Undersquare engines typically are, proportionally, shorter in length, heavier, and taller than equivalent oversquare ones, which is one of the reasons why this type of engine is not generally used.

Many British automobile companies used undersquare designs through the 1950s, largely because of a motor tax system that taxed cars by their cylinder bore. Therefore, many of the most famous cars of that era use this design. This includes the Austin A-Series engine and many Nissan derivatives.

The Chrysler Slant-6, in the most common 225 cubic inch (3.7 L) version, is a massively undersquare engine with a 3.40" (86 mm) bore and a 4.125" (105 mm) stroke, producing most of its power right on the peak of its torque curve. The achilles heel of this engine, otherwise known for its exceptional durability, is being over-revved by inexperienced drivers. Red line for a factory engine is under 4,500 rpm; red line with aftermarket connecting rods is about 5,500 rpm. On the other hand, a well-maintained Slant-6 can be made to idle as low as 75 rpm (though this is *not* a recommended speed, neither the alternator nor the oil pump will function adequately). In some circles, the Slant-6 is nicknamed "The Stump-Puller" for its diesel-like low-speed torque. Appropriate gearing and driving skill is required for performance use.

Willys also used mostly undersquare engines, in fact the L134 and F134 engines, with their fairly small 3.125 inch (79.4 mm) bore and 4.375 inch (111.1 mm) stroke, are probably the most undersquare engines ever built.

Nowadays, undersquare engines tend to be quite rare, but this form of engine is still used in some applications. For example, a modern 8.4 liter Valmet 645 inline-6 tractor diesel engine is a longstroke/undersquare engine, but has an output of over 300 horsepower (224 kW) with turbocharger and intercooler. The popular Mazda Miata also uses an undersquare engine.

[GTR]

oversquare lebih potensial buat tuning, secara bore besar means luas penampang valves intake&exhaust (penampang kubah ruang bakar) otomatis lebih besar daripada underquare engine yg korbankan luas penampang valves ke panjang stroke; ini juga merupakan kekurangan utama underquare engine yg posting di atas tadi ketinggalan.
Kubah ruang bakar yg luas, memungkinkan besar ukuran valves lebih flexible => saluran bahan bakar bisa dibuat besar/lancar lebih flexible.

tapi ini semua secara general saja, hasil/karakter output akhir masih relatif terhadap faktor setting2 lainnya.

kekurangan oversquare engine:
kalo ring piston sudah aus, konsumsi oli lebih cepat drpd undersquare engine.
relatif kurang cocok untuk mesin kapasitas kecil, krn sifat umum yg less torque tadi.

karakter undersquare engine:
pd rpm rendah-menengah; flow/kecepatan aliran bahan bakar masuk (mengisi) ke silinder (yg panjang tp bore nya kecil) pd langkah hisap jadi relatif lebih tinggi, ini relatif memberi advantages juga ke torsi (seperti prinsip lenght manifold intake).

modern mass production gasoline car yg max power nya kisaran 6000rpm pada umumnya juga membatasi panjang stroke s/d di sekitar 90an - 100mm, karena limit piston speed.

@bro GTR n Imsus2C, kira2 kl untuk pemakaian sehari2 lebih bgs mana ya? kl gw liat dimajalh autobild xtrail mesin MR20 stroke panjang akselerasi lbh baik drpd QR20 stroke pendek.
kalau engine oversquare n square kalau ditune buat balap lebih bgs drpd undersquare?

mengenai vibrasi, gw coba gigi netral xtrail2.5(under square) diinjek gas ampe 2000 rpm geteran mesinnya lbh berasa drpd crv 2.0. bgt juga city (under square)geterannya lumayan berasa ketimbng crv. mungkin apa pengrh perbedaan bore n stroke ?

[imsus2c]

sip...

sudah dijelasin ma om GTR diatas kan...?

kalo yg dimaksud "pemakaian sehari-hari" itu adalah untuk city-cruising alias banyak stop & go, dari teori teknis lebih cocok ke undersquare engine secara tenaganya sudah ada di puaran bawah. Sedikit banyak berpengaruh ke akselerasi dan konsumsi bbm...CMIIW

[uch]

ada analogi "kunci roda" utk memahami stroke ini. pertama kali buka baut roda, kita perlu kunci yg panjang karna lbh bertenaga. setelah 2-3 baut berputar, kita memendekkan pegangan kunci karna butuh putaran yg lebih cepat.
gitu jg dgn mesi mobil. kalo mencari tenaga di rpm rendah berarti stroke hrs panjang.

[maxx]

An engine that has equal bore and stroke has a bore/stroke value of 1.
For example an engine which has both 95 mm bore and stroke has a bore/stroke value of:
95 mm / 95 mm = 1.00
This type of engine is called a square engine. Usually engines that have a bore/stroke ratio of 0.95 to 1.04 are referred as square engines

GL type mesin termasuk kategori Square engine
HR15DE [GL 1.5] >> Bore x stroke = 78.0 x 78.4 = 0.995
MR18DE [GL 1.8] >> Bore x stroke = 84.0 x 81.1 = 1.035

Undersquare engine dan oversquare engine sudah jelas karakternya, kalo square engine bisa dibilang mixed antar karakter kedua Undersquare engine dan oversquare engine.

Ada yg bisa perjelas karakter square engine?

[ZombiEE]

makin lama makin binunnnn....

[imsus2c]

An engine that has equal bore and stroke has a bore/stroke value of 1.
For example an engine which has both 95 mm bore and stroke has a bore/stroke value of:
95 mm / 95 mm = 1.00
This type of engine is called a square engine. Usually engines that have a bore/stroke ratio of 0.95 to 1.04 are referred as square engines

GL type mesin termasuk kategori Square engine
HR15DE [GL 1.5] >> Bore x stroke = 78.0 x 78.4 = 0.995
MR18DE [GL 1.8] >> Bore x stroke = 84.0 x 81.1 = 1.035

Undersquare engine dan oversquare engine sudah jelas karakternya, kalo square engine bisa dibilang mixed antar karakter kedua Undersquare engine dan oversquare engine.
Ada yg bisa perjelas karakter square engine?

buat yg positive-thinking, bilangnya:
mesin yg efisien, akselerasi ga malu-maluin, top speed ngejar, hemat bbm, mudah perawatan....

buat yg negative-thinking bakal respon:
mesin nanggung...ragu2....akselerasi lemot top speed mlorott....susah dituning...boros dan emisi tinggi....wakakaka



............. ..................

jadi inget ada anekdot, saat seorang cendekiawan yg super pinter tapi sayang item, buncit dan jelek...didatengi cewek yg mulus aduhai, tinggi semampai tapi agak o'on, si cewek bilang:
Kawinlah denganku...!!!
Kenapa?
Memperbaiki keturunan...
Kok bisa?
Lha iya...kan kamu pinter tapi jelek, aku cakep tapi bodoh, anak kita kan nantinya sempurna, cakep dan pinter...
Ya kalo bisa, ...tapi kalo sebaliknya?
Sebaliknya gimana?
Gimana anak kita nanti kalo jadinya item, buncit, jelek...bodoh lagi...

.................................

[maxx]

untung nissan ga bego2 amat ya... hasilnya positive thinking lebih ke positive thinking dari pada negative-nya

[avansa]

Magsud banget kalau di hubung hubungkan dengan yang molek dan aduhai.

[GTR]

yup betul.
klo produsen sampai set berbeda ukuran keduanya (bore & stroke) dlm setiap varian kapasitas mesin, at least mereka ini memang memperhatikan ukuran yg paling ideal utk masing2 kapasitas mesin nya, walaupun maybe ga bs share internal parts misalnya piston related parts.
mirip mesin jaman lancer dan-gan GTi 1600cc dan 1800cc, yg dibikin beda (bore jg stroke) agar ideal performance nya di masing2 kapasitas tsb walaupun sebasis mesin.

untung nissan ga bego2 amat ya... hasilnya positive thinking lebih ke positive thinking dari pada negative-nya

[remedusakti]

yup betul.
klo produsen sampai set berbeda ukuran keduanya (bore & stroke) dlm setiap varian kapasitas mesin, at least mereka ini memang memperhatikan ukuran yg paling ideal utk masing2 kapasitas mesin nya, walaupun maybe ga bs share internal parts misalnya piston related parts.
mirip mesin jaman lancer dan-gan GTi 1600cc dan 1800cc, yg dibikin beda (bore jg stroke) agar ideal performance nya di masing2 kapasitas tsb walaupun sebasis mesin.

untung nissan ga bego2 amat ya... hasilnya positive thinking lebih ke positive thinking dari pada negative-nya

ada patokan rasio ideal ga bro, misal untuk tipe oversquare maximum berapa ? tipe undersquare brp ?

Trus kalau buat tuning pasang turbo lebih sip tipe oversquare, maybe ?

[GTR]

gasoline, kalo bore blm tau juga harus berapa, kalo stroke kalo ga salah sekitar 100mm utk modern engine yg max output nya di rpm kisaran 6000rpm, otherwise, tambah silinder.

karena itu juga, sebagian produsen tambahkan turbocharger drpd tuning N/A kalo tingkatkan output instant, krn tuning N/A harus manaikkan rpm begitu tinggi; kl turbo, power bisa diraih pada rpm relatif lebih rendah alias rpm masih bisa sama dari sblm pakai turbo.
so, kalo tuning turbo sepertinya mesin long-stroke masih lebih oke2 saja, beda dgn tuning N/A yg harus perhatikan piston speed limit.

contoh ilustrasinya; max rpm mesin stock S2000-AP1(F20c, 2000cc) yg 9200rpm diturunkan jadi 8300rpm utk yg versi stock S2000-AP2(F22c, 2200cc, krn long-stroke version), jadinya hasil akhir speed piston keduanya adalah sama.

[ZombiEE]

oic oic...thanks bro atas penjelasannya..kalo git..it's safe to assume that, kalo long stroke engine piston dan stang nya kudu kuwat?

[GTR]

yup, karena makin panjang setangnya (tergantung over/under square), makin mudah "ditekuk" drpd pendek tergantung beban/dorongan tonase piston dan setang akibat tenaga yg dihasilkan.

[ZombiEE]

pantesan seri qr dari nissan gak bisa hig rev yah?hehehehe

[nescafe]

hmm.. bukannya mesin kijang (K series) kurang bisa untuk high rev?

[GTR]

kan karena valvetrain masih ohv, nes...
mirip juga dgn corvette.

kalo nissan QR itu bukannya ada yg "agak" hi-rev @6600 yah di model Sentra SE-R V-spec?

[ZombiEE]

itu lhor...spec-v kan sama dgn yg di x-trail kan?hehehehe

[remedusakti]

kan karena valvetrain masih ohv, nes...
mirip juga dgn corvette.

kalo nissan QR itu bukannya ada yg "agak" hi-rev @6600 yah di model Sentra SE-R V-spec?

bro gtr, btw itu seri QR berapa yah? kalau QR20 bkn tipe undersquare tp kalau QR25 tipe undersquare.

Bro2 ada yang tau ndak neh tentang compact balancer shaft ? ini diklaim nissan untk mengurangi getaran. adakah kaitannya dengn stroke yang panjang ?

[ZombiEE]

qr25 bro...

kalo ga salah balance shaft ini dipake buat counter getaran mesin qr 25 ini..soale ini mesin large displacement dgn silinder 4...cmiiw